This application claims the benefit of Korean Utility Model Application Not. 98-24474, filed Dec. 8, 1998, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a motor for rotating an upper drum, which is provided on a top surface of the upper drum and a top portion of a stationary shaft, in a head drum apparatus for use in a magnetic tape recording and reproducing apparatus; and, more particularly, to a head drum apparatus capable of reducing the number of components and the manufacturing steps by using a single surface printed circuit board (xe2x80x9cPCBxe2x80x9d), thereby decreasing the production cost, enhancing the manufacturing efficiency, and increasing the productivity thereof.
2. Description of the Related Art
Conventionally, a shaft-rotating type head drum apparatus has been employed in a magnetic tape recording and reproducing apparatus. In the shaft-rotating type head drum apparatus, a rotating shaft is pressed and fitted into an upper drum and a lower drum is rotatably mounted on a lower portion of the rotating shaft. A motor is attached to the bottom surface of the lower drum and activated to rotate the shaft and hence the upper drum. A head provided in the upper drum records or reproduces a signal to or from a magnetic tape.
However, the head drum apparatus of the shaft-rotating type has two freedom degrees and does not fully overcome resonant vibration problems, so that it cannot remove the likelihood of its malfunction due to the resonant vibration upon the rotation of the upper drum.
Recently, in order to solve the above problems, a shaft-fixed type head drum apparatus has been proposed. The typical constitution of the shaft-fixed type head drum assembly will now be described.
As shown in FIGS. 1 and 2, a general shaft-fixed type head drum apparatus of a magnetic tape recording and reproducing apparatus comprises: a lower drum 1 having a recessed portion la formed therein, a stationary shaft 2 pressed and fitted into a center hole of the lower drum 1, a stationary transformer 3 attached to the bottom surface of the lower drum 1, the stationary transformer 3 having a plurality of concentric channels 3a formed on the top surface thereof, a plurality of stator coils 4 wound in the respective channels 3a, an upper drum 7 rotatably coupled to the stationary shaft 2 via bearings 5 and 6 fixed on a middle portion and an upper portion of the stationary shaft 2, respectively, a rotary transformer 8 attached to a bottom surface of the upper drum 7 such that a gap is formed between the rotary and the stationary transformers 8 and 3, the rotary transformer 8 having a plurality of concentric channels 8a on the bottom surface thereof, a plurality of lines of rotor coils 9 wound in the respective channels 8a of the rotary transformer 8, a head assembly 20 and a full-width erasing head assembly 30 fixed to the bottom surface of the upper drum 7 by means of screws 10, a signal transmitting means for transmitting the signals between the rotor coils 9 of the rotary transformer 8 and the head assembly 20 and the full-width head assembly 30, and a drum motor provided on the top portion of the stationary shaft 2 and the top surface of the upper drum 7.
The signal transmitting means uses a flexible printed circuit (xe2x80x9cFPCxe2x80x9d) 11. Mounted to a portion of the pattern formed on the FPC is a ceramic condenser (hereinafter referred to as xe2x80x9cchipxe2x80x9d) which acts as a filter tuning the frequency band within the band of a full-width erasing head 32.
The head assembly 20 and the full-width erasing head assembly 30 are provided with a video head 22 and the full-width erasing head 32 on the leading ends of head bases 21 and 31, respectively. The head assembly 20 and the full-width erasing head assembly 30 also have PCBs 23 and 33 with desired patterns on the bottom surfaces thereof, respectively. The video head 22 and the full-width erasing head 32 are electrically connected to the PCBs 23 and 33, respectively.
On the other hand, the drum motor includes a motor stator 40 fixed to the top portion of the stationary shaft 2 and a motor rotor 50 fixed to the top surface of the upper drum 7.
Specifically, the motor stator 40 is fitted on the top portion of the stationary shaft 2 and includes a boss 42 into which a set screw 41 is radially screwed, a PCB 43 secured to the bottom surface of the boss 42, motor stator coils 44 mounted on the top surface of the PCB 43, and a back yoke 45 mounted on the PCB 43 to cover the motor stator coils 44. The motor rotor 50 includes a plate 52 fixed to the top surface of the upper drum 7 by means of a plurality of screws 51 and a motor magnet 53 attached to the upper surface of the plate 52.
Formed on the bottom surface of the PCB 43 are a pulse generator(xe2x80x9cPGxe2x80x9d) pattern P for controlling the position of the video head 22 mounted to the upper drum 7 and a frequency generator(xe2x80x9cFGxe2x80x9d) pattern F for performing a regional control as a detail control of the PG pattern P, as shown in FIGS. 3 to 5.
The FG pattern F has a wave form which is circumferentially disposed around the center thereof and has two lines, an inner line and an outer line. The PG pattern P is located at a portion on one side of the FG pattern F.
In order to connect a connection pattern C1 and C3 formed one surface of the PCB 43 with a connection pattern C2 and C4 formed on the other surface, it is necessary to form an another FG pattern Fxe2x80x2 and an another PG pattern Pxe2x80x2 on the top surface of the PCB 43, which is opposite to the bottom surface on which the FG pattern F and the PG pattern P are formed. The FG patterns F and Fxe2x80x2 are connected to each other through a through hole 43a and the PG patterns P and Pxe2x80x2 are connected to each other through a through hole 43b. The terminals of the FG pattern Fxe2x80x2 and the PG pattern Pxe2x80x2 are connected to the connection patterns C2 and C4, respectively.
In the above conventional shaft-fixed type head drum apparatus, the upper drum 7 is rotated by an electromagnetic activation of the drum motor provided at the top portion of the stationary shaft 2 and the top portion of the upper drum 7, the head 22 of the upper drum 7 reproduces or records the signals from or to a tape (not shown) traveling around the outer peripheral surfaces of the upper and the lower drums 7 and 1, and the full-width erasing head 32 erases the information (signals) recorded on the tape.
On the other hand, the signals from the head 22 and the full-width erasing head 32 are transmitted through in turn the FPC 11 connected to the respective PCBs 23 and 32, the rotor coils 9 of the rotary transformer 8 and the stator coil 4 of the stationary transformer 3, to a controller (not shown) or vice versa.
At this time, since the PG patterns P and Pxe2x80x2 and the FG patterns F and Fxe2x80x2 are formed on the PCB 43 of the motor stator 40, a motor servo function for controlling the position and section of the upper drum 7 is performed.
However, in the conventional shaft-fixed type head drum apparatus described above, the PCB having both surfaces of which the PG patterns P and Pxe2x80x2 and the FG patterns F and Fxe2x80x2 are formed is employed, and it is difficult to manufacture the bisurface PCB, thereby resulting in an increased production cost due to the need for the additional back yoke 45, a decreased operation efficiency and a poor productivity thereof.
It is, therefore, an object of the present invention to provide a motor of a head drum apparatus capable of reducing a number of components and manufacturing steps by using monosurface printed circuit board (xe2x80x9cPCBxe2x80x9d) thereby decreasing the production cost, enhancing the manufacturing efficiency and increasing the productivity thereof.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In accordance with the present invention, there is provided a head drum apparatus comprising: a lower drum; a stationary shaft pressed and fitted into a center hole of the lower drum; an upper drum rotatably coupled to the stationary shaft via at least one bearing; a rotor magnet secured via a plate to the upper drum; a boss fixed to the top portion of the stationary shaft by means of a set-screw; a PCB mounted to the boss such that it is opposite to the rotor magnet, the PCB having a PG pattern, an FG pattern, connection patterns and jump patterns formed on one surface thereof, the PG pattern and the FG pattern being connected to the respective connection patterns via the respective jump patterns; and motor stator coils mounted to the PCB.
Preferably, the motor stator coils are mounted to the patterns such that they are opposite to the rotor magnet.